Process and apparatus for quenching tubular metal articles



Sept. 24, 1957 H. E. M cRAY 2,807,272 PROCESS AND APPARATUS FOR QUENCHING TUBULAR METAL ARTICLES Filed June 1, 1953 3 Sheets-Sheet l IL/ IN V EN TOR.

I?! BY Maw/v Sept. 24, 1957 H. E. M CRAY PROCESS AND APPARATUS FOR QUENCHING TUBULAR METAL ARTICLES Filed June 1, 1953 75 Sheets-Sheet 2 INVENTOR.

nited States Patent Ofiice 2,807,272 Patented Sept. 24, 1957 PROCESS AND APPARATUS FOR QUENCHING TUBULAR METAL ARTICLES Harold E. McCray, Pampa, Tex., assignor to Cabot Shops, Inc., Boston, Mass., a corporation of Massachusetts Application June 1, 1953, Serial No. 358,580 4 Claims. Cl. 134-167) structure becomes austenitic and is then cooled at a rate sufliciently rapid to achieve at least 90% conversion to martensite structure without formation of intermediate baim'te, pearlite or ferrite structures. The cooling to the martensite (Ms) starting temperature of 590 F. must thus be accomplished within a critical period of time, for gun steel within 160 to 180 seconds and even more rapidly for reduced alloy content steels, and ultimate cooling to a surface temperature of about 150 F. must in most cases be completed within a total period of less than minutes to insure that the steel in the interior of the article will be cooled to at least the 420 F. required for 90% martensite structure. Treatment is then completed in the draw furnace.

The generally accepted method of rapidly cooling metal articles is to immerse the article in a liquid, usually Water, until the temperature is reduced to the required value. Naturally, the hot article will warm the quench liquid so that fresh, cool liquid must constantly be circulated through the quench zone. However, merely adding water to one portion of a quench tank and withdrawing used Water from another portion is not suflicient to quench long tubular articles of variable diameter and wall thickness. Reflection will readily reveal that water introduced into the bottom of a quench tank, for instance, will be heated during its travel to the top and hence will have a slowerquenching rate at the upper end than at .the lower end of the article.

'The problems suggested above are indicative of the many existing in this art. They have been surmounted but not without dilficulty and heretofore the quenching of large metal tubes of nonuniform diameters has been a complicated and rather delicate procedure. a

It is the principal object of my invention to provide an apparatus for the quenchingof such tubes which is eflicient and'uncomplicated and which is easily operated with accurately reproducible results It is another object of this invention to provide a quench fonmetal tubes, particularly of nonuniform diamete'rs and wall thicknesses, which is largely free from the defects of prior known quenches. 1

Another object of this invention is to provide apparatus including novel means for supplying quench liquid to the bore of the tube and for regulating the volume of liquid applied to various areas of the tube.

Another object is to provide apparatus which has associated therewith a novel means for supporting the article to be quenched therein.

It is also an object of this invention to provide a novel apparatus for quenching steel tubes in which martensite structure can regularly be obtained.

It is another object of this invention to provide a novel process for quenching metal tubes.

In achieving the objects of my invention I provide a vertically disposed overflow tank and a quench tube or tank therein having conduits respectively to supply water or other liquid to the bottom of the quench tube and to carry the water from the bottom of the overflow tank. The quench tube may be provided with ports having adjustable closures in the side wall at one or more points intermediate its extremeties although such ports are not always necessary. At the bottom of the quench tube is a spring supported nozzle disposed in the axis of the quench tube on which the tubular article to be quenched is seated. A third conduit is connected to the nozzle.

It should be noted, and this is a feature of my invention, that the size of the quench tube is variable depending upon the size and shape of the article to be quenched For best results the diameter of the quench tube should be only slightly greater than that of the tube being cooled therein and, if desired, may be contoured to approximate the profile of the inserted tube.

My invention will now be described with reference to the accompanying drawings of a preferred embodiment of the apparatus, in which Fig. 1 is a view in vertical cross section of the apparatus showing a gun tube, partly in cross section, in position therein,

Fig. 2 is a detail view in vertical cross section of the bore quench nozzle assembly of the apparatus shown in Fig. 1, and

Fig. 3 is a chart of the isothermal transformation curves for a typical high yield steel.

The apparatus of my invention comprises an overflow tank 10 vertically disposed in which is provided a smaller tube or tank 12, generally referred to herein as the quench tube. In the side wall of quench tube 12 at a convenient location intermediate its ends several ports 14 are advantageously provided at spaced positions around its circumference having an adjustable cylindrical cover 16 freely movable along the length of the quench tube and being suitably supported as by cables 18 passing over sheaves 20 and by counterweights 22.

Connected into the bottom of quench tube 12 is a conduit 24 through which water or other cooling liquid is supplied at desired flow rates and temperatures. Centered in conduit 24 at the bottom end of the quench tube is bore quench 26 shown in detail in Fig. 2, having a liquid supply pipe 28. A third conduit 30 is provided in the bottom of overflow tank 10 to remove used quench liquid. Pumps, valves, liquid cooling towers, cranes and the like, which constitute well known auxiliary equipment, are not shown although all such are provided in conjunction with the apparatus of this invention.

The article to be quenched, here shown as a gun tube 32 is centered in quench tube 12, the breech end 33.

Wedges 40are inserted between the ring and the test metal ledge. The bail is then available for lifting by a crane in the usual manner.

Nozzle assembly 26, which is one of the novel features of this invention, is shown in detail in Fig. 2. It comprises a fixed central conduit 52 and a tip or nozzle 34 supported on helical spring 42 seated on an abutment or 3 base 44 appropriately fixed in place, as by welding around the outer wall of conduit 52. Concentric sleeves 46 and 47 are secured to nozzle 34 to inhibit leakage of high pressure fiuid around thelower portion of the nozzle when in extended position. Thus, sleeves 46 and 47 are free to ride up and down With'the nozzle, and rings 48 and 50 secured to sleeve 46 and conduit 52 respectively provide a substantially leak proof seal in the manner of piston rings in the cylinders of internal combustion engines. The nozzle 34 is here illustrated as being substantially fully retracted but its length of travel upward islirnited only by the expansibility of the spring 42 and the distance between seal rings 48 and 50.

Referring now to Fig. 3, the isothermal transformation curves for "G54-2- steel havingthe following alloy composition is'shown: r

I 0.31 Mn 0.76 Si 0.30 P 0.009 S 0.013 Ni 3.07 Cr 1.22 Mo 0.49 A1 0.031

It is ordinarily necessary that the steel be heated to above the critical point (As), this being where a visible amount of austenite (at least 0.1%) starts to form in a manner somewhat analogous to the formation of icecrystals in water. The A3 point varies with different steel compositions of course, being for instance 1460 F. for a 1019 (0.19 carbon, 0.92 Mn) steel. Heating to above the critical point is required in order that the steel will have a uniformly austenitic structure before quenching.

As a study of Fig. 3 will show, it is essential that the steel be quenched very rapidly in order that the cooling curve will pass to the left of the nose of the bainite curve in order to achieve the desired 90% martensite, or maximum obtainable structure. The slope of the cooling curve is very steep and for steel of the formula given 'above the temperature must be reduced almost 1000 F. in no more than 180 seconds (3 minutes). For a steel tube having a thickness of four inches for at least a part of its length v very efiicient cooling is essential. This is provided by the novel apparatus of this invention.

The operation of the apparatus of this invention is as follows: With quench tube 12 having a diameter only a few inches greater than that of the tubular article to be quenched the article is lowered into the tube with its bore centered on nozzle 34 and to a distance such that the spring 42 is almost completely compressed. Cooling liquid, ordinarily water, is pumped through conduits 24 and 28 at high velocity.

Although ports 14 are not required for, satisfactory quenching of most articles I have foundthat use of ports 14 may be beneficial to eliminate completely the danger of cracking the metal in the upper and smaller end of a tapered article. Since the thinner walls will be cooled more rapidly than the thicker walls I have found it advantageous with some steel compositions to utilize ports 14 as follows.

At the start of the quench cover 16 is lowered to close ports 14 completely. After running the quench for a suflicient time to cool the upper, thinner metal to the desired temperature cover 16 is raised so that the bulk of the peripheral quench water flows into the outer tank through the ports instead of past the treated article.

However, as I have said, the use of these ports is in most cases optional.

For a gun tube having the composition described in connection with Fig. 3 the flow of water was as follows: Through bore--1000 gals/min, velocity 47.3 ft./sec.

Around barrel-4800 gals./min., velocity 40 ft./sec.

At these volumes and velocities the cooling curve coincided with the required cooling curve C of Fig. 3.

After completingthe quench to about 150-200 F. on the outside (which ensures cooling the center to below the 420 F. necessary for martensite) the article is withdrawn from quench tube 12 and placed immediately in a draw furnace in the usual manner.

During quench the metal naturally contracts which would tend to lift the bottom end of the article from the bore nozzle. However, by means of the bore quench assembly of my invention nozzle 34 remains firmly seated throughout the quench. j

Having thus described my invention, I claim:

1. Apparatus for quenching tubular metal articles comprising a vvertically disposed tank having an outlet conduit at the bottom, a vertically disposed quench tube having a diameter only slightly larger than the article to be quenched therein positioned within said first mentioned tank, a conduit adapted to supply a liquid to the bottom of saidinner tube, a spring loaded nozzle within said'conduit adapted,to engage the bore of the article to be quenched, a second conduit adapted to supply liquid to said nozzle and means to, suspend a tubular metal article within said quench tube.

2. The apparatus of claim 1 further. characterized by ports in the side wall of the quench tube and an adjustable closure therefor.

3. The apparatus of claim 1 in which the vertically disposed quench tube'is contoured tov approximate the profile of the article to be quenched therein.

4. In apparatus for quenching tubular articles comprising in cornbinationan overflow tank, a quench tube of lesser diameter therein adapted to contain a tubular article to be quenched and means to supply cooling fluid at substantial velocity to the quench tube and to withdraw fluid from the overflow tank; a bore quench for the article tobe quenched axially aligned in the base of the quench tube, said bore quench comprising a fixed central conduit, a seal ring secured therearound, a nozzle axially aligned with said conduit, a pair of concentric sleeves secured to the nozzle and depending therefrom, theinner sleeve being in sliding contact with the seal ring secured around the conduit and having a seal ring secured therearound in sliding contact with the conduit wall, a fixed abutment around said conduit and a helical spring coiled aroundthe inner sleeve and within the outer sleeve depending from the nozzle maintained under compression between said abutment and nozzle, and means to supply cooling fluid at substantial velocity to the'bore quench.

. References Cited in .the'file of thispaterit UNITED STATES PATENTS 620,224 Bubser Feb. 28, 1899 2,216,698 Arey et al Oct. 1, 1940 2,371,117 Somes Mar. 6,1945 2,441,628 Grifliths et al May 18, 1948 2,531,942- Lee Nov. 28, 1950 2,531,943 Lee Nov. 28, 1950 2,547,053 Somes et a1 Apr. 3, 1951 2,638,909 Hiatt May 19, 1953 2 ,664,901 Gehr Ian. 5,1954 

